1. Field of the Invention
The present invention relates to three-dimensional (3D) memory devices, and more particularly to methods to fabricate such memory devices.
2. Description of Related Art
High density memory devices are being designed that comprise arrays of flash memory cells, or other types of memory cells. In some examples, the memory cells comprise thin film transistors which can be arranged in 3D architectures.
In one example, a 3D memory device includes a plurality of stacks of poly crystalline active strips separated by insulating material. The active strips can act as bit lines or word lines. The 3D memory device can include a plurality of word lines structures arranged orthogonally over the plurality of stacks of active strips which act as bit lines. Alternatively, the 3D memory device can include a plurality of bit line structures arranged orthogonally over the plurality of stacks of active strips which act as word lines. Memory cells including charge storage structures are formed at cross-points between side surfaces of the active strips in the plurality of stacks and the word lines structures or bit line structures. Channel regions of memory cells are formed in the active material strips. 3D memory devices using small dimension memory cells, including vertical gate (VG) 3D NAND memory devices, can present challenges in manufacturing such memory devices as stacks in the memory devices include more layers of memory cells.
It is desirable to improve methods in manufacturing such memory devices.